Oh, you meant an _instance_, not a data structure. Sorry.
More specifically, a single instance. Instead of having something like
a per-object file symbol bcache as was done with GDB, there would just
be a single global bcache (and it would never shrink).
elf-strtab has a property which I'm not sure you really need in GDB,
as it slow things down. It attempts to do suffix merging, ie. if you have
p = "abcde" and q = "cde", r = "cde", s = "abcde" strings,
then p = "abcde", q = p + 2, r = q, s = p. Storing strings in a hashtable
is certainly cheaper for CPU time than this.